Retail Antitheft Scanners Interfere with Heart Pacemakers
April 11, 2000 (Atlanta) -- Electronic antitheft system scanners, frequently used by retailers to curb shoplifting, can disturb the function of a variety of pacemakers, according to a report in the March issue of the journal PACE.
Even so, it's safe for people with implanted pacemakers to walk through antitheft system scanners, but they should avoid standing too close, says study author Jacques Mugica, MD, an electrophysiologist at the Surgical Center Val d'Or in Saint-Cloud, France.
Because pacemaker interference by electronic antitheft systems has been controversial, French researchers exposed more than 200 pacemaker patients to two leading systems in a medical examining room. Before and after exposure, the pacemaker's function was analyzed. Additionally, an electrocardiogram (EKG) was taken to record the heart's function during exposure for up to 30 seconds. The study participants had three kinds of pacemakers made by seven manufacturers.
The data showed that the antitheft devices interfered with pacemaker function in 17% of the participants. The "intermittent alarm" type of antitheft system showed twice as many interferences as the "continuous alarm" type of system.
The most common type of pacemaker disturbances were those that interfered with the pacemakers' ability to regulate and sense the heart's rate and rhythm. This problem lasted throughout the exposure. The exposures did not cause problems with the pacemakers' programming, and only one patient developed heart palpitations.
The lead author compares the effects of the systems' magnetic fields to routine testing of pacemakers using a magnet, which is known to be safe for brief periods. During magnet testing, a physician places a magnet over the pacemaker, which turns off the device and allows the physician to observe the functioning of the heart itself.
"We observed the same type of pacing abnormalities as previous studies, though the incidence was much lower," says Mugica. "The use of commercial antitheft systems, to mimic real life, may account for the differences."
What about other electronic devices? "Pacemaker patients are often anxious about cell phones and microwave ovens, but the risk of interference is very low," says Jonathan Langberg, MD, director of the electrophysiology lab and professor of medicine at Emory University in Atlanta. Langberg notes that pacemakers are now designed to filter out electromagnetic interference.
Many pacemakers now are programmed to prevent sensing disturbances, according to Langberg. "But even in older models, interference results in a missed beat or two and doesn't cause any symptoms," he says. "Only MRI scans and radiation therapy to the chest cause serious pacemaker problems."
Langberg says the effect of antitheft systems on implanted defibrillators, an internal device designed to shock the heart if an abnormal rhythm occurs, is not yet known.